TY - JOUR

T1 - Markers of protein oxidation

T2 - different oxidants give rise to variable yields of bound and released carbonyl products

AU - Headlam, Henrietta A

AU - Davies, Michael Jonathan

PY - 2004

Y1 - 2004

N2 - Exposure of proteins to radicals in the presence of O2 gives both side-chain oxidation and backbone fragmentation. These processes can be interrelated, with initial side-chain oxidation giving rise to backbone damage via transfer reactions. We have shown previously that alkoxyl radicals formed on the C-3 carbons of Ala, Val, Leu, and Asp residues undergo beta-scission to give backbone alpha-carbon radicals, with the release of the side- chain as a carbonyl compound. We now show that this is a general mechanism that occurs with a wide range of oxidants. The quantitative significance of this process depends on the extent of oxidation at C-3 compared with other sites. HO*, generated by gamma radiolysis, gave the highest total carbonyl yield, with protein-bound carbonyls predominating over released. In contrast, metal ion/H2O2 systems, gave more released than bound carbonyls, with this ratio modulated by EDTA. This is ascribed to metal ion-protein interactions affecting the sites of initial oxidation. Hypochlorous acid gave low concentrations of released carbonyls, but high yields of protein-bound material. The peroxyl radical generator 2,2'-azobis(2-amidinopropane) hydrochloride, and a peroxynitrite generator, 3-morpholinosydnonimine hydrochloride, gave lower overall carbonyl yields, with released carbonyls predominating over protein-bound species similar to that observed with metal ion/H2O2 systems.

AB - Exposure of proteins to radicals in the presence of O2 gives both side-chain oxidation and backbone fragmentation. These processes can be interrelated, with initial side-chain oxidation giving rise to backbone damage via transfer reactions. We have shown previously that alkoxyl radicals formed on the C-3 carbons of Ala, Val, Leu, and Asp residues undergo beta-scission to give backbone alpha-carbon radicals, with the release of the side- chain as a carbonyl compound. We now show that this is a general mechanism that occurs with a wide range of oxidants. The quantitative significance of this process depends on the extent of oxidation at C-3 compared with other sites. HO*, generated by gamma radiolysis, gave the highest total carbonyl yield, with protein-bound carbonyls predominating over released. In contrast, metal ion/H2O2 systems, gave more released than bound carbonyls, with this ratio modulated by EDTA. This is ascribed to metal ion-protein interactions affecting the sites of initial oxidation. Hypochlorous acid gave low concentrations of released carbonyls, but high yields of protein-bound material. The peroxyl radical generator 2,2'-azobis(2-amidinopropane) hydrochloride, and a peroxynitrite generator, 3-morpholinosydnonimine hydrochloride, gave lower overall carbonyl yields, with released carbonyls predominating over protein-bound species similar to that observed with metal ion/H2O2 systems.

KW - Acetone

KW - Aldehydes

KW - Formaldehyde

KW - Glyoxylates

KW - Hydrogen Peroxide

KW - Metals

KW - Oxidants

KW - Oxidation-Reduction

KW - Proteins

KW - Serum Albumin, Bovine

U2 - 10.1016/j.freeradbiomed.2004.02.017

DO - 10.1016/j.freeradbiomed.2004.02.017

M3 - Journal article

C2 - 15082071

VL - 36

SP - 1175

EP - 1184

JO - Free Radical Biology & Medicine

JF - Free Radical Biology & Medicine

SN - 0891-5849

IS - 9

ER -